Due to a lock elision bug present in older versions of the glibc
package on Ubuntu 16.04 for POWER, you must upgrade the glibc
package to at least glibc2.23-0ubuntu5 before running MongoDB.
Systems with older versions of the glibc package will experience
database server crashes and misbehavior due to random memory
corruption, and are unsuitable for production deployments of MongoDB

Important

Before you attempt any upgrade, please familiarize yourself with the
content of this document.

To upgrade an existing MongoDB deployment to 3.4, you must be
running a 3.2-series release.

To upgrade from a version earlier than the 3.2-series, you must
successively upgrade major releases until you have upgraded to
3.2-series. For example, if you are running a 3.0-series, you must
upgrade first to 3.2before you can upgrade to 3.4.

Before beginning your upgrade, see the Compatibility Changes in MongoDB 3.4 document to
ensure that your applications and deployments are compatible with
MongoDB 3.4. Resolve the incompatibilities in your deployment before
starting the upgrade.

Before upgrading MongoDB, always test your application in a staging
environment before deploying the upgrade to your production
environment.

It is recommended that after upgrading, you allow your deployment to
run without enabling these features for a burn-in period to ensure
the likelihood of downgrade is minimal. When you are confident that
the likelihood of downgrade is minimal, enable these features.

Run the setFeatureCompatibilityVersion command against the admin database: